6.The size of sand grains should pass through 4.75mm IS sieve and should be entirely retained on 75 micron IS sieve.

Coarse aggregate

Functions:

·Coarse aggregate makes solid and hard mass of concrete with cement and sand.

·It increases the crushing strength of concrete.

·It reduces the cost of concrete, since it occupies major volume.

Requirements: Coarse aggregate used may be crushed stone, gravel and broken bricks.

Crushed stone: It is an excellent coarse aggregate provided. It is obtained by crushing granite, sand stone and close grained lime stone.

Crushed granite chips are commonly and advantageously used in reinforced cement concrete.

Broken bricks well burnt and over burnt bricks are broken into suitable size and used as aggregate. It should be well watered before its use. Broken bricks are used as aggregate for concrete in foundations and under floors.

But generally crushed stone is only used as coarse aggregate.

Water

The water is used in concrete plays an important part in the mixing, laying compaction setting and hardening of concrete. The strength of concrete directly depends on the quantity and quality of water is used in the mix.

Functions:

1.Water is only the ingredient that reacts chemically with cement and thus setting and hardening takes place.

2.Water acts as a lubricant for the aggregate and makes the concrete workable.